Dr. Zakir: As far as fasting is concerned if a lady is having her menstrual periods according to a Hadith which is mentioned in
Sahih Al Bukhari Vol no. 3 in the Book of Fasting Hadith no. 1951
Hazrat Aisha, (may Allah be pleased with her), who is the wife of Prophet Muhammad (saws), she said when she was asked this question that do we have to make up for the fast or does the fast break while menstruating? So she said that
"When we used to fast and when we used to have our menstruations during the month of Ramadhaan she used to say that during the month of Ramadhaan when we had our menstruation, the Prophet asked us to make up for the fast but did not ask us to make up for the Salaah."
So based on the ruling of Muhammad (saws) which was narrated to us by his wife Hazrat Aisha, (may Allah be pleases with her), so making up for the prayer is not a requirement but making up for the fast is a requirement. So if a woman has a menstrual cycle or post natal bleeding, she cannot continue with the fast, the fast breaks. If she has in between in the day, she will have to break the fast or even if the menstruation starts just a few minutes before sunset, she'll have to break the fast, the fast is not valid. But if menstruation stops just before Fajr then she can keep the fast. But if the menstruation stops just a few minutes after Fajr she cannot keep the fast and she will have to make up the fast later on after Ramadhaan.
The reason why the fasting breaks when a woman has her menstrual period or post natal bleeding is because of a lot of blood flows out and Allah (swt) does not over burden the woman. So it's a grace from Allah (swt), He does not want to make it difficult because when blood flows out and then after that if you say that you should not take in nourishment, you should not take food, it's an overburdening so because of that Allah (swt) has excused the women that she need not fast, but she has to make up later on.
The reason she has to make up the fast later on which she does not have to do in Salaah because Salaah is supposed to be prayed everyday of your life minimum 5 times a day. So there is no question once she misses her Salaah may be for 5 days, 6 days, 7 days whatever it is, when will she make up? Because she is suppose to offer Salaah everyday of her life but fasting is only compulsory in the month of Ramadhaan. So if she misses for 7 days in the month of Ramadhaan, she can very well compensate for it after the month of Ramadhaan is over. Therefore according to my thinking, according to my understanding that's the reason Allah (swt) and our beloved Prophet Muhammad (saws) has told that the women should not make up for her Salaah if she misses during her menstrual period but she has to make up for the fast she misses during the month of Ramadhaan.